This invention concerns the selective preparation of ethanol and methyl acetate from methanol and synthesis gas. More particularly, the invention concerns the reaction of methanol and synthesis gas under heterogeneous reaction conditions in the presence of a catalyst of rhodium and iron on alumina into which is diffused an alkaline metal compound to produce ethanol and methyl acetate.
The reaction of methanol with hydrogen and carbon monoxide to produce ethanol and other oxygen-containing organic compounds is known and disclosed in the prior art. For example, U.S. Pat. No. 4,133,966 discloses a process for the selective formation of ethanol which comprises contacting methanol, hydrogen and carbon monoxide with a catalyst system comprising cobalt acetylacetonate, a tertiary organo Group VA compound of the Periodic Table, a first promoter comprising an iodine compound and a second promoter compound comprising a ruthenium compound.
U.S. Pat. No. 3,285,948 entitled HALIDES OF RUTHENIUM AND OSMIUM IN CONJUNCTION WITH COBALT AND IODINE IN THE PRODUCTION OF ETHANOL FROM METHANOL, issued to Butter on Nov. 15, 1966, teaches a method for producing alcohols in which any source of cobalt soluble in the reaction medium which will yield a cobalt carbonyl or hydrogen cobalt carbonyl under the reaction conditions can be used. In addition, an iodine promoter is employed, for example, I.sub.2, or alkali metal iodines. A secondary promoter is also employed, i.e., ruthenium halide or osmium halide. High selectivity is described as better when the secondary promoter is used in combination with the primary promoter and other reactants.
U.S. Pat. No. 4,013,700, entitled CATALYTIC PROCESS FOR POLYHYDRIC ALCOHOLS AND DERIVATIVES, issued to Cawse on Mar. 22, 1977, discloses a process for the preparation of polyhydric alcohols, their ether and ester derivatives, and oligomers of such alcohols. In particular, these alcohols and their derivatives are produced by reacting the oxides of carbon and hydrogen in the presence of a quaternary phosphonium cation and a rhodium carbonyl complex at elevated temperature and pressure.
Another process is set forth in U.S. Pat. No. 3,248,432, entitled PROCESS FOR THE PRODUCTION OF ETHYL ALCOHOL, issued to Riley et al on Apr. 26, 1966, which relates to a process for the production of ethyl alcohol by the interaction of methanol, carbon monoxide and hydrogen at elevated temperature and pressure in the presence of a cobalt catalyst and an iodine promoter. Examples of suitable cobalt sources are described as any water-soluble source of cobalt, for example, the cobalt carbonyls, the lower salts of alkanoate cobalt, such as cobalt acetate, cobalt formate, cobalt propionate, and the like.
U.S. Pat. No. 2,623,906, entitled PREPARATION OF ORGANIC HYDROXY-CONTAINING COMPOUNDS BY REACTING ALCOHOLS WITH CARBON MONOXIDE AND HYDROGEN, issued to Gresham on June 16, 1948, relates to a procedure for synthesizing mono and poly functional oxygen-containing organic compounds by the reaction of alcohols, carbon monoxide and hydrogen. Catalysts described as suitable for use include various cobalt compounds, for example, cobalt carbonyl, cobalt carbonyl hydride, metallic cobalt, and organic and inorganic cobalt salts.
Dutch Pat. No. 760,6138 entitled PROCESS FOR THE FORMATION OF ETHANOL FROM METHANOL AND SYNTHESIS GAS, issued to Shell International Research on June 8, 1976, relates to a process for producing alcohols which utilizes any soluble cobalt source which can generate a cobalt carbonyl or hydrocarbonyl by reaction with the synthesis gas. For example, sources of cobalt suitable for use are cobalt iodide or cobalt metal from which ions can be generated in situ. Organic salts of cobalt such as cobalt acetate, formate, or propionate are described as especially good sources, an iodide or bromide promoter is also utilized. In addition, the use of a tertiary phosphine is described as affording improved selectivity to the formation of alcohols.
U.S. application Ser. No. 437,141 filed Jan. 28, 1974, now abandoned, discloses a process for manufacturing acetic acid, its lower alkyl esters, ethanol and lower alkyl aldehydes by contacting a reaction mixture of an oxide of carbon and hydrogen with a solid metal catalyst from the group of rhodium, ruthenium, cobalt, osmium, iridium and platinum. In one embodiment disclosed therein, methanol is co-fed with hydrogen and carbon monoxide over a supported rhodium catalyst with the reported result that productivities of the process were improved with the addition of methanol to the fed gas.
U.S. application Ser. No. 541,660 filed Jan. 16, 1975, now abandoned, discloses a process for the selective preparation of ethanol by continuously contacting a synthesis gas reaction mixture containing hydrogen and carbon monoxide with a catalyst of rhodium and iron dispersed on a particulate support.
So far as applicant is aware, however, no process is provided for selectively preparing ethanol and methyl acetate by contacting a mixture of methanol, carbon monoxide and hydrogen with a heterogenous catalyst comprising rhodium and iron supported on an alumina support containing an alkaline metal. Unexpectedly, applicant has discovered that large amounts of ethanol and methyl acetate can be produced by contacting such a gaseous reaction mixture with the catalyst composition disclosed herein.